lighting & Yafray but not smooth shadow

http://imagebin.ca/img/Ac48x2M.jpg

the picture have not smooth shadow i don’t know why ?

http://imagebin.ca/img/9UQBgWWY.png

Lighting point

http://imagebin.ca/img/UU6pHDI.png

render setting

http://imagebin.ca/img/63hud23.png

http://imagebin.ca/img/dLQeJVrh.png

http://imagebin.ca/img/y2TsE5a.png